The predominant view about memory formation states that a consolidation process stabilizes newly acquired traces until they are safely stored in the brain. However, during the last ten years evidence has accumulated to indicate that, upon retrieval, consolidated memories are rendered again vulnerable to the action of metabolic blockers, notably protein synthesis inhibitors. This has led to the hypothesis that memories are reconsolidated at the time of retrieval, and that this requires protein synthesis in different brain regions. Here we will address the consolidation-reconsolidation debate and discuss some controversial issues about the reconsolidation hypothesis, in particular the biological role of this process.